Alert archive / Iowa / Flash Flood Warnings in 2017

Flash Flood Warning 7, NWS Sioux Falls, SD

October 6, 2017Plymouth County, Iowa; Dixon County, Nebraska; Union County, South Dakota

NWS Sioux Falls, SD issued this flash flood warning at Oct 6, 2017, 10:15 AM CDT for Plymouth County, Iowa; Dixon County, Nebraska; Union County, South Dakota. It was in force for 3 hr. No storm report in the archive falls inside the area while it was in force.

The area

The outline as issued.

The facts

Issued: Oct 6, 2017, 10:15 AM CDT (15:15 UTC)
Expired: Oct 6, 2017, 1:15 PM CDT
In force: 3 hr
Issued by: NWS Sioux Falls, SD
Area: Storm-based polygon
Flood severity: None

Counties Plymouth County, IA, Dixon County, NE, Union County, SD

The radar

The Sioux Falls radar (KFSD), 105 km from the middle of the area, began a volume at 15:17 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Omaha, NE (KOAX), launched 12:00Z, 3.3 hours before the alert went out and 150 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 54 J/kg
Mixed-layer CIN: -146 J/kg
Mixed-layer LCL: 473 m above ground
0-6 km bulk shear: 50 kt
0-1 km storm-relative helicity: 109 m²/s²
0-3 km storm-relative helicity: 106 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.0

Open this sounding in Storm Lab

The text

As transmitted.

991 
WGUS53 KFSD 061515
FFWFSD
IAC149-NEC051-SDC127-061815-
/O.NEW.KFSD.FF.W.0007.171006T1515Z-171006T1815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/

BULLETIN - EAS ACTIVATION REQUESTED
Flash Flood Warning
National Weather Service Sioux Falls SD
1015 AM CDT FRI OCT 6 2017

The National Weather Service in Sioux Falls has issued a

* Flash Flood Warning for...
  Western Plymouth County in northwestern Iowa...
  Central Dixon County in northeastern Nebraska...
  Southern Union County in southeastern South Dakota...

* Until 115 PM CDT

* At 1014 AM CDT, Doppler radar indicated thunderstorms producing 
  heavy rain across the warned area. Up to two and a half inches of 
  rain has already fallen in Newcastle Nebraska. Flash flooding is 
  expected to begin shortly.

* Some locations that will experience flooding include...
  Ponca, Elk Point, Akron, Merrill, Jefferson, Newcastle,
  Martinsburg, Ponca State Park, Brunsville and Westfield.

Additional rainfall amounts of 1 to 2 inches are possible in the 
warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 4264 9701 4271 9683 4271 9681 4272 9680
      4291 9633 4270 9620 4252 9670 4252 9672
      4251 9672 4245 9690

$$

Weisser

2 follow-up statements

895 
WGUS73 KFSD 061650
FFSFSD

Flash Flood Statement
National Weather Service Sioux Falls SD
1150 AM CDT FRI OCT 6 2017

IAC149-NEC051-SDC127-061815-
/O.CON.KFSD.FF.W.0007.000000T0000Z-171006T1815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Plymouth IA-Dixon NE-Union SD-
1150 AM CDT FRI OCT 6 2017

...THE FLASH FLOOD WARNING REMAINS IN EFFECT UNTIL 115 PM CDT FOR
WESTERN PLYMOUTH...CENTRAL DIXON AND SOUTHERN UNION COUNTIES...

At 1149 AM CDT, Doppler radar indicated showers and isolated 
thunderstorms producing moderate rain across the warned area. Flash 
flooding is expected as 2 to 4 inches of rain has fallen in the past 
3 hours.

Some locations that will experience flooding include...
Ponca, Elk Point, Akron, Merrill, Jefferson, Newcastle, Martinsburg,
Ponca State Park, Brunsville and Westfield.

Additional rainfall amounts of a half inch are possible in the 
warned area.

PRECAUTIONARY/PREPAREDNESS ACTIONS...

Turn around, don't drown when encountering flooded roads. Most flood
deaths occur in vehicles.

&&

LAT...LON 4264 9701 4271 9683 4271 9681 4272 9680
      4291 9633 4270 9620 4252 9670 4252 9672
      4251 9672 4245 9690

$$

Weisser

578 
WGUS73 KFSD 061732
FFSFSD

Flash Flood Statement
National Weather Service Sioux Falls SD
1232 PM CDT FRI OCT 6 2017

IAC149-NEC051-SDC127-061741-
/O.CAN.KFSD.FF.W.0007.000000T0000Z-171006T1815Z/
/00000.0.ER.000000T0000Z.000000T0000Z.000000T0000Z.OO/
Plymouth IA-Dixon NE-Union SD-
1232 PM CDT FRI OCT 6 2017

...THE FLASH FLOOD WARNING FOR WESTERN PLYMOUTH...CENTRAL DIXON AND
SOUTHERN UNION COUNTIES IS CANCELLED...

The heavy rain has ended. Flooding is no longer expected to pose a 
threat. Please continue to heed any remaining road closures. An 
additional quarter to half inch will be possible the next few hours 
with additional rainfall possible during the evening.

LAT...LON 4264 9701 4271 9683 4271 9681 4272 9680
      4291 9633 4270 9620 4252 9670 4252 9672
      4251 9672 4245 9690

$$

Weisser

The office that day

Everything else NWS Sioux Falls, SD issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Oct 6, 7:14 AM CDT	Severe Thunderstorm Warning	FSD	Plymouth	46 min
Oct 6, 3:56 PM CDT	Flash Flood Watch	FSD	Cherokee, Ida, Plymouth, Woodbury	11 hr
Oct 6, 6:51 AM CDT	Severe Thunderstorm Warning	FSD	Dixon	24 min

Nearby

Flash Flood Warnings in Iowa, 2017 Flash Flood Warnings in Nebraska, 2017 Flash Flood Warnings in South Dakota, 2017 Every flash flood warning in 2017

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.